An example of component placement is in the field of die placement. In current die-bond equipment that is designed for fast (order die/second) and accurate (order 10 micron) placement of dies on a substrate the accuracy depends on a lot of machine parameters. The strategy for reaching an accurate placement is generally as follows:
1. A bond head consists of a camera looking downward (to view the substrate) and a pick-up tool.
2. Pick a die from a donor substrate (e.g. wafer).
3. Move the die to an upward looking camera to measure the orientation of the die with respect to the pick-up tool, and correct any misalignment.
4. Move the bond head to the placement position on the substrate. Use the image of the camera to get position information of the bond head.
5. Move the bond head to position the die above the placement position.
6. Place the die.
Step 5 is required as the tool and the camera cannot be in the same position on the bond head. So after measuring the placement position, a step is required during and after which no verification of the position is possible. This ‘blind’ step is about 5 to 10 cm long, based on the size of the camera unit and the tool. The accuracy of this blind step depends on the accuracy of the bearings and metrology and requires a complex calibration scheme. So in practice the overall placement accuracy may still be too low. A need arises to further reduce the placement error.